There is growing interest in high-precision machining to fabricate miniaturized parts for medical devices, micro-satellites, microfluidics, and the optics and electronics industries, with meso-scale machine tool systems (MMTS) which utilize tools with diameters ranging from 10 to 500 μm. Such MMTS technologies complement standard silicon micro-machine fabrication processes with the ability to directly produce true, three-dimensional structures with high accuracy, low cost, and short cycle time. One of the key methods in MMTS technology is micro-end milling. Precision machining with micro-end milling is strongly influenced by the choice of tool materials. Tungsten carbide (WC) with cobalt binder (WC—Co) is widely used as a standard material. However, it suffers from a number of drawbacks such as limited and unpredictable operational life, rapid degradation of performance with use due to tool fatigue and wear, difficulty in machining adhesive metals such as aluminum and copper, and poor surface finish.
To combat the drawbacks of the use of WC—Co as a tool material for MMTS technologies, one possible solution is to coat the WC—Co with harder materials such as diamond. Unfortunately, conventional diamond films contain relatively large crystallites, placing a limitation on the minimum thickness of the films and making such film practical only for larger tools (e.g., tools having a diameter of 500 μm or greater). (See, for example, Jackson, et al., Proc. Instn. Mech. Engrs., Vol. 217, p. 77 (2003).
Bruhne et al., have reported depositing nanocrystalline diamond films on tungsten carbide cutting tools. (See, Bruhne et al., Rev. Adv. Mater. Sci., Vol. 10, p. 224 (2005).) However, the minimum reported thickness of such films is 10 μm, which the authors admit renders the tool incapable of cutting. Only by using a reactive ion etch (RIE), were the authors able to reduce the thickness of the film.